Studies on the Reduction of the Nitro Group in 4-Nitroindazoles by Anhydrous SnCl₂ in Different Alcohols

SnCl2/EtOH-Mediated Synthesis of Novel 4-Ethoxy- and 4-Chloroindazoles Bearing Sulfonamide Moieties

“…The ability of SnCl 2 , in alcoholic solution, to form the corresponding 4-chloroindazoles 4a-d, was observed for the first time during the reduction of 1-alkyl-5-nitroindazole. In the course of our previous studies on the reduction of 4-, 6-and 7-nitroindazoles [10][11][12][13] with stannous chloride in different alcohols the chlorination was not observed.…”

“…We thus, have reported the synthesis of 7-alkoxy-and 4-alkoxyindazole derivatives via the reduction of 4-, 6-and 7-nitroindazoles in the presence of anhydrous SnCl 2 in various alcohol solvents, followed by the coupling of the newly formed amine with arylsulfonyl chlorides in pyridine [10][11][12][13][14][15][16][17] . We selected arylsulfonyl chloride as a protective agent of aminoindazole because in our previous study, we observed significant degradation of aromatic primary amine.…”

“…In view of its inherent properties such as reusability, greater selectivity, operational simplicity, non-corrosiveness, low cost and ease of isolation, several groups have accomplished efficient syntheses of different heterocyclic compounds employing the reduction of nitro derivatives with stannous chloride [6][7][8][9] . Our research program during the last ten years has been focused on the synthesis of heterocyclic compounds using anhydrous SnCl 2 as reductive reagent [10][11][12][13][14][15][16][17] .…”

Synthesis and Antitumor Activity of Some Substituted Indazole Derivatives

“…We reported previously the reduction of some nitroindazoles, with anhydrous SnCl 2 in various alcohols, in the presence of arylsulfonyl chlorides and pyridine . Thus, we observed a new kind of transformation: 4‐, 6‐, and 7‐nitroindazoles, by the action of SnCl 2 /EtOH, gave 4‐ or 7‐ethoxy aminoindazoles, probably via an oxidative nucleophilic substitution of hydrogen (ONSH), along with the expected 4‐, 6‐, and 7‐aminoindazoles.…”

Synthesis of Novel Substituted Indazoles via Nucleophilic Substitution of Hydrogen (SNH)

“…The synthesis of substituted indazole has been already accomplished by various chemical methods , but very few examples of nucleophilic substitution reactions in the indazole series have been reported . Previously, our group has reported the synthesis of 4‐ and 7‐alkoxyindazoles via a nucleophilic substitution of hydrogen at position 4 and 7 of indazole using the reduction of 4‐, 6‐, and 7‐nitroindazoles with SnCl 2 in different alcohols . Continuing our study on the nucleophilic substitution reactions of hydrogen in nitroindazole, in this work we investigated the reaction of N ‐alkyl‐7‐nitroindazoles with arylacetonitriles in a basic methanol solution.…”